Coin-cell type batteries are known in the art. They can be used for just about any electronic device or circuit where small size is needed, e.g., because of the needed portability of the device, and power consumption demands are low.
Coin-cell type batteries are thus employed in a wide variety of hand-held electronic gadgets and controls, such as cameras, garage-door openers, remote controls, medical monitors (e.g., sensors for sensing body temperature when placed in the mouth, ear, or other body cavity), hearing aids, wristwatches, and the like. Coin-cell type batteries may also commonly be found where a tiny backup power source is needed to power a critical circuit element, such as volatile memory circuits or the system clock, within a large computer system.
Recent enhancements made to coin-cell type batteries, such as switching to a lithium-based chemistry, have increased the capacity of the coin-cell battery so that the battery can be made thinner while still providing the output capacity previously available in only larger, especially thicker, batteries. Such enhancements have allowed the devices in which the enhanced batteries are used to be made smaller than has heretofore been possible. However, the power output capacity of such batteries is still severely limited. That is, such enhanced batteries are still not capable of powering any type of electronic circuit where the instantaneous output current drawn from the battery—needed to power the circuit so that it can reliably perform its intended function—must be more than a few milliamps for more than a second or two.
The problem inherent in coin-cell type batteries, including the enhanced coin-cell batteries employing lithium-based chemistry, is that they have a relatively high output impedance, often as high as 100 to 200 ohms. This high output impedance causes the output voltage of the battery to drop below its nominal voltage value as a function of the instantaneous output current drawn from the battery as a function of ohm's law, V=IR, where V is voltage, I is current, and R is (in this instance) impedance. Thus, if the nominal output voltage of the battery is 3 volts, and if output impedance of the battery is 100 ohms, and the output current drawn from the battery is 6 milliamps (ma), then the battery voltage will drop from 3 volts to 3−(6 ma×100 ohms)=3.0−0.6=2.4 volts, or a 20% drop in the output voltage of the battery. Such a dramatic drop in battery voltage could easily cause the circuit(s) powered by the coin-cell battery to malfunction.
For an implantable medical device—where reliable operation of the device is critical for the efficacy of the device as well as the safety of the patient within whom the device is implanted—such a 20% drop in battery voltage is not acceptable. Hence, it has long been a key design constraint that batteries used in an implantable medical device must have a battery impedance that is very low, usually less than 1.0 ohm, e.g., 0.3 to 0.5 ohms.
To obtain a battery with an impedance less than 1 ohm requires a custom-made battery. Custom-made batteries having a very low impedance have thus become the “standard” for use in implantable medical devices. This is especially the case for devices that produce stimulation pulses, such as a pacemaker or a neurostimulator, where the stimulus current produced by the device must produce a stimulus pulse of sufficient intensity (e.g., where “intensity” is typically measured in current or voltage amplitude) for the stimulus pulse to achieve its intended function of stimulating muscle tissue or nerves in the area where the stimulus pulse is applied to body tissue.
Custom-made batteries having a very low impedance suitable for use in an implantable medical device are known in the art. However, such custom-made batteries tend to be quite large and very expensive. The size of the battery is dictated primarily by the basic battery chemistry and structure needed to achieve the necessary low battery impedance.
Thus, it is seen that because coin-cell batteries inherently have a high battery impedance—on the order of 100 to 200 ohms—they have never been considered for use in implantable medical devices, except perhaps extremely simple applications, such as monitoring internal body temperature, where the current demands placed on the battery are very low, e.g., less than 100 microamperes (0.1 ma).
What is needed, therefor, is electronic circuitry, and methods for operating such circuitry, that allows a small, thin, low cost, high impedance battery, such as a coin-cell type battery, to be used in an implantable medical device, such as an implantable neurostimulator.
Traditional acupuncture and acupressure has been practiced in Eastern civilizations (principally in China, but also in other Asian countries) for at least 2500 years. It is still practiced today throughout many parts of the world, including the United States and Europe. Acupuncture is an alternative medicine that treats patients by insertion and manipulation of needles in the body at selected points. See, Novak, Patricia D. et al (1995). Dorland's Pocket Medical Dictionary (25th ed.), Philadelphia: (W.B. Saunders Publisher), ISBN 0-7216-5738-9. The locations where the acupuncture needles are inserted are referred to as “acupuncture points” or simply just “acupoints”. The location of acupoints in the human body has been developed over thousands of years of acupuncture practice, and maps showing the location of acupoints in the human body are readily available in acupuncture books or online. For example, see, “Acupuncture Points Map,” found online at: http://www.acupuncturehealing.org/acupuncture-points-map.html. Acupoints are typically identified by various letter/number combinations, e.g., L6, S37. The maps that show the location of the acupoints may also identify what condition, illness or deficiency the particular acupoint affects when manipulation of needles inserted at the acupoint is undertaken.
References to the acupoints in the literature are not always consistent with respect to the format of the letter/number combination. Some acupoints are identified by a name only, e.g., Tongli. The same acupoint may be identified by others by the name followed with a letter/number combination placed in parenthesis, e.g., Tongli (HT5). Alternatively, the acupoint may be identified by its letter/number combination followed by its name, e.g., HT5 (Tongli). The first letter typically refers to a body organ, or other tissue location associated with, or affected by, that acupoint. However, usually only the letter is used in referring to the acupoint, but not always. Thus, for example, the acupoint ST40 is the same as acupoint Stomach 40 which is the same as ST-40 which is the same as ST 40 which is the same as Fenglong. For purposes of this patent application, unless specifically stated otherwise, all references to acupoints that use the same name, or the same first letter and the same number, and regardless of slight differences in second letters and formatting, are intended to refer to the same acupoint.
An excellent reference book that identifies all of the traditional acupoints within the human body is WHO STANDARD ACUPUNCTURE POINT LOCATIONS IN THE WESTERN PACIFIC REGION, published by the World Health Organization (WHO), Western Pacific Region, 2008 (updated and reprinted 2009), ISBN 978 92 9061 248 7 (hereafter “WHO Standard Acupuncture Point Locations 2008”). The Table of Contents, Forward (page v-vi) and General Guidelines for Acupuncture Point Locations (pages 1-21) of the WHO Standard Acupuncture Point Locations 2008 are incorporated herein by reference. Moreover, the above-cited portions of the WHO Standard Acupuncture Point Locations 2008 reference book may be found as Appendix D in Applicant's earlier-filed U.S. patent application Ser. No. 13/598,582, filed Aug. 29, 2012, which application, including its appendices, are also incorporated herein by reference.
As an alternative to traditional acupuncture, some have proposed applying moderate electrical stimulation at selected acupuncture points through needles that have been inserted at those points. See, e.g., http://en.wikipedia.org/wiki/Electroacupuncture. Such electrical stimulation is known as electroacupuncture (EA). According to Acupuncture Today, a trade journal for acupuncturists: “Electroacupuncture is quite similar to traditional acupuncture in that the same points are stimulated during treatment. As with traditional acupuncture, needles are inserted on specific points along the body. The needles are then attached to a device that generates continuous electric pulses using small clips. These devices are used to adjust the frequency and intensity of the impulse being delivered, depending on the condition being treated. Electroacupuncture uses two needles at a time so that the impulses can pass from one needle to the other. Several pairs of needles can be stimulated simultaneously, usually for no more than 30 minutes at a time.” “Acupuncture Today: Electroacupuncture”. 2004 Feb. 1 (retrieved on-line 2006 Aug. 9 at http://www.acupuncturetoday.com/abc/electroacupuncture.php).
U.S. Pat. No. 6,735,475, issued to Whitehurst et al., discloses use of an implantable miniature neurostimulator, referred to as a “microstimulator,” that can be implanted into a desired tissue location and used as a therapy for headache and/or facial pain. The microstimulator has a tubular shape, with electrodes at each end.
Other patents of Whitehurst et al. teach the use of this small, microstimulator, placed in other body tissue locations, including within an opening extending through the skull into the brain, for the treatment of a wide variety of conditions, disorders and diseases. See, e.g., U.S. Pat. No. 6,950,707 (obesity and eating disorders); U.S. Pat. No. 7,003,352 (epilepsy by brain stimulation); U.S. Pat. No. 7,013,177 (pain by brain stimulation); U.S. Pat. No. 7,155,279 (movement disorders through stimulation of Vagus nerve with both electrical stimulation and drugs); U.S. Pat. No. 7,292,890 (Vagus nerve stimulation); U.S. Pat. No. 7,203,548 (cavernous nerve stimulation); U.S. Pat. No. 7,440,806 (diabetes by brain stimulation); U.S. Pat. No. 7,610,100 (osteoarthritis); and U.S. Pat. No. 7,657,316 (headache by stimulating motor cortex of brain).
Techniques for using electrical devices, including external EA devices, for stimulating peripheral nerves and other body locations for treatment of various maladies are known in the art. See, e.g., U.S. Pat. Nos. 4,535,784; 4,566,064; 5,195,517; 5,250,068; 5,251,637; 5,891,181; 6,393,324; 6,006,134; 7,171,266; and 7,171,266. The methods and devices disclosed in these patents, however, typically utilize (i) large implantable stimulators having long leads that must be tunneled through tissue over an extended distance to reach the desired stimulation site, (ii) external devices that must interface with implanted electrodes via percutaneous leads or wires passing through the skin, or (iii) inefficient and power-consuming wireless transmission schemes. Such devices and methods are still far too invasive, or are ineffective, and thus are subject to the same limitations and concerns, as are the previously described electrical stimulation devices.
From the above, it is seen that there is a need in the art for a less invasive device and technique for electroacupuncture stimulation of acupoints that does not require the continual use of needles inserted through the skin, or long insulated wires implanted or inserted into blood vessels, for the purpose of treating an illness or deficiency of a patient.